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A nonlinear thermodynamic Sharpe-Schoolfield-Ikemoto (SSI) model has been applied to temperature-dependent development of some arthropods and other ectotherms. The most important parameter estimated by the SSI model is the intrinsic optimum temperature (Φ), which is the temperature at which the probability of an enzyme being in its active state is maximal. It has been also suggested that Φ authentically represents the optimal ambient temperature for fitness in ectotherms. We applied the SSI model to larvae of four aquatic decapod crustacean species distributed in cold, temperate, and tropical waters for understanding thermal adaptation in decapods. As a result, TΦ's estimates for the larvae corresponded to the optimum temperatures for larval survival/growth. The estimates also changed in accordance with the geographical distribution of the stages, species, and populations studied, i.e., 6.91-9.06 °C for cold-water species and 19.68-27.00 °C for temperate and tropical species. It would be useful to examine the relationship between changes in geographical distribution with temperature Φ and population size for a better understanding of population fluctuations under global climate change. Additionally, stable aquaculture production could be enhanced if the temperature conditions of each life history stage were controlled at Φ. [ABSTRACT FROM AUTHOR]

We investigated the effects of male and female body size on the mating behavior and spawning success of the Japanese spiny lobster Panulirus japonicus (von Siebold, 1824) under laboratory conditions in order to develop broodstock management techniques. The lobsters were divided into three body-size groups of each sex based on the maximum sizes observed in landings and the minimum sizes at sexual maturity. Mating behavior was observed by video recording 39 pairs in nine combinations among the large-, medium-, and small-size groups of each sex. Mating behavior was observed in 21 pairs, 20 females laid eggs, and clutch size and egg fertilization rates were determined. The effects of male and female body size (continuous variable) on mating behavior were also analyzed. Mating behavior was categorized into four phases: approach, upright posture, copulation, and separation. Smaller males tended to have difficulty manipulating and holding larger females. The total number of copulations per couple and duration of a single copulation were higher in smaller males, suggesting that females require multiple matings to increase the probability of fertilization. The rate of spawning success tended to increase when females mated with larger males. Fertilization rates were unaffected by male or female body size and were 90.0-100%, except in one pair of a smallsize male and a medium-size female (3.5%). Clutch size was significantly affected by female but not male body size. Our mating experiments suggest that small-size males are not recommended for use as broodstock for larviculture. [ABSTRACT FROM AUTHOR]

We evaluated the genetic diversity and demographic history of the terrestrial hermit crabs Birgus latro and Coenobita brevimanus using mtDNA COI sequence data (573 bp). Tissue samples from 163 individuals of B. latro and 63 individuals of C. brevimanus were collected at 11 and four localities in the North-Western Pacific Region, respectively. Haplotype diversity was high and similar in B. latro (0.8809) and C. brevimanus (0.9222). Nucleotide diversity was higher in C. brevimanus (0.01088) than in B. latro (0.00404). No genealogical structure was observed in haplotypes of B. latro whereas four haplotype clades were found in C. brevimanus. Weak but significant genetic population structure with the isolation by distance was detected in B. latro, but no genetic population structure was observed in C. brevimanus, likely because of the small number of sampling localities for the latter. Demographic history analyses suggested that B. latro and C. brevimanus had different histories of population expansion. Birgus latro experienced population expansion once during the glacial period when sea levels were relatively lower in the late Pleistocene. Conversely, it was inferred that haplotype clades of C. brevimanus diverged during or near the interglacial period when sea levels were relatively higher, and their population expansion and remixing occurred through the glacial periods in the late Pleistocene. [ABSTRACT FROM AUTHOR]

The effect of water temperature on the growth of juvenile snow crabs Chionoecetes opilio (Fabricius, 1788) was investigated in laboratory culture experiments. Laboratory-born juveniles were cultured from instar I to VIII at four temperatures (approximately 1, 3, 5 and 8°C). The growth indices (size increments at moulting in mm and in % of premoult carapace width) were significantly higher in crabs reared at 5°C than in those reared at other temperatures. The relationship between the mean temperature (T ) and intermoult period (D) of each instar was described by the heat summation theory equation: D = K/(T --α). The thermal constant K is the summation of the effective temperature for development (above the threshold temperature, α) up to a selected biological end point. The thermal constant tended to increase and the threshold temperature tended to decrease with increasing mean premoult carapace width of each instar, reaching asymptotes of 1573 day-degrees and -4.7°C, respectively. Size- and temperature-dependent growth models were developed for snow crab juveniles. [ABSTRACT FROM AUTHOR]

Populations of the coconut crab, Birgus latro (Linnaeus, 1767), have been depleted by primarily overharvest. The aim of this study was to develop artificial propagation technologies for the restocking and conservation of this species: it is a terrestrial hermit crab with aquatic larvae. Megalopae (post-larvae stage) were group cultured for six months with access to both "land" and "sea" areas (trial 1). In addition, shell-carrying juveniles aged one month were group cultured on land until the age of 13 or 24 months (trial 2). Furthermore, juveniles that had abandoned their gastropod shells were cultured individually and their moult and growth was monitored. The survival rates of animals ranged from 26-55% in trial I, and they grew to a mean thoracic length (TL) of approx. 1 mm. In trial 2, the juveniles grew to a mean TL of approx. 4 mm at age 24 months. The juveniles changed their gastropod shells for larger ones according to their growth based on their body width. The juveniles found soon after abandoning their gastropod shells varied in size (2.5-8.6 mm TL), age (15-26 months old), and the degree of the formation of pleonal tergal plates. The juveniles without shells moulted 5-6 times during the culture period of 9-20 months. Two survivors grew to 6.8 mm TL and 11.9 mm TL at an age of 24 and 37 months, respectively. The body colour pattern of the juveniles was retained through successive moults. Our results demonstrated the feasibility of artificial production of the coconut crab juveniles and the utility of using natural marks to monitor their growth and migration after being released in the wild. [ABSTRACT FROM AUTHOR]

Populations of the coconut crab, Birgus latro (Linnaeus, 1767), have been depleted by overharvesting and environmental degradation. The aim of this study was to develop artificial propagation technologies for the restocking and conservation of this species. Coconut crabs migrate from the sea to land as megalopae, carrying gastropod shells. We examined the effects of sea-water availability and the timing of their involuntary migration from sea to land on the survival and moulting of megalopae and juveniles by culturing them individually in containers with dry "land" but with or without aquatic "sea areas." The schedule of their involuntary migration to the land in the test containers was set at ages of 5 and 10 days after metamorphosis to the megalopal stage, and at ages between 12 and 16 days, when the megalopae walked steadily while wearing a shell. The treatments did not affect the moulting of the animals. The animals survived in the containers with seawater areas. In contrast, all those in the containers without sea areas died, and severe mortality occurred after the animals moulted to the crab stage, suggesting that water availability may protect the animals from desiccation in air during and after ecdysis. Old megalopae (10 days old) appeared to be more active than young megalopae (5 days old) in walking and manipulating shells at first landing, although the three different schedules of migration to land did not affect the survival of the animals. Our results highlight the importance of water availability in culturing coconut crab juveniles. [ABSTRACT FROM AUTHOR]